Timing and Characterization of the Change in the Redox State of Uranium in Precambrian Surface Environments: A Proxy for the Oxidation State of the Atmosphere

The redox-sensitive geochemical behavior of uranium permits the use of Th/U ratios as a geochemical proxy for the oxidation state of the atmosphere and oceans during sedimentary processes. Due to the effects of post-depositional uranium mobility on Th/U ratios during events involving oxygenated fluids, direct measurements of Th/U ratios are often misleading, but the whole rock Pb isotope composition may be used to determine a sample¡¦s apparent time-integrated Th/U ratio (ƒÛa) and the timing associated with the onset of the U-Th-Pb geochemistry. Rare earth element (REE) concentrations were determined by isotope dilution mass spectrometry to evaluate the influence of multiple provenance components and potential mobility of Th, U, and Pb during post-depositional processes on the Th/U ratio. The Pb isotope compositions and REE concentrations were determined for six Paleoproterozoic sedimentary sequences, which were the focus of previous studies involving the timing of the rise of atmospheric oxygen. The Mount McRae Shale, Huronian Supergroup, and Zaonezhskaya Formation have been interpreted as experiencing post-depositional alteration (perhaps associated with orogenic events) due to Pb-Pb ages that are younger than the likely depositional age and observed fractionation of REE in chondrite normalized REE patterns and interelement REE ratios (e.g. La/Nd, La/Yb, Eu/Eu*). Similar geochemical proxies have been interpreted as sedimentary geochemical features of the Timeball Hill Formation, Hotazel Formation, and Sengoma Argillite Formation. This study of Paleoproterozoic sedimentary units constrains the onset of U-Th decoupling, most likely due to the onset of oxidative weathering conditions, began by 2.32 Ga, the latest

Are scientists really doing science? : Personal reflections on the NIH grant system

This brief essay summarizes some personal thoughts on the NIH grant system. The thoughts arise in part from my experience as a dissenter from scientific orthodoxy, and in part from my experience as a member of several workshops convened to assess and fix problems with the NIH and NSF grant systems.Sociedad Argentina de Fisiologí

Core Formation in Giant Gaseous Protoplanets

Sedimentation rates of silicate grains in gas giant protoplanets formed by disk instability are calculated for protoplanetary masses between 1 M_Saturn to 10 M_Jupiter. Giant protoplanets with masses of 5 M_Jupiter or larger are found to be too hot for grain sedimentation to form a silicate core. Smaller protoplanets are cold enough to allow grain settling and core formation. Grain sedimentation and core formation occur in the low mass protoplanets because of their slow contraction rate and low internal temperature. It is predicted that massive giant planets will not have cores, while smaller planets will have small rocky cores whose masses depend on the planetary mass, the amount of solids within the body, and the disk environment. The protoplanets are found to be too hot to allow the existence of icy grains, and therefore the cores are predicted not to contain any ices. It is suggested that the atmospheres of low mass giant planets are depleted in refractory elements compared with the atmospheres of more massive planets. These predictions provide a test of the disk instability model of gas giant planet formation. The core masses of Jupiter and Saturn were found to be ~0.25 M_Earth and ~0.5 M_Earth, respectively. The core masses of Jupiter and Saturn can be substantially larger if planetesimal accretion is included. The final core mass will depend on planetesimal size, the time at which planetesimals are formed, and the size distribution of the material added to the protoplanet. Jupiter's core mass can vary from 2 to 12 M_Earth. Saturn's core mass is found to be ~8 M_Earth.Comment: Accepted for publication in Icaru

Molecules, Water, and Radiant Energy: New Clues for the Origin of Life

We here examine the putative first step in the origin of life: the coalescence of dispersed molecules into a more condensed, organized state. Fresh evidence implies that the driving energy for this coalescence may come in a manner more direct than previously thought. The sun’s radiant energy separates charge in water, and this free charge demonstrably induces condensation. This condensation mechanism puts water as a central protagonist in life rather than as an incidental participant, and thereby helps explain why life requires water

Von Verteidigern und Entdeckern

Dieses Open-Access-Buch bietet eine Einführung in den Identitätskonflikt zwischen Verteidigern und Entdeckern. Basierend auf einer Studie mit 5000 Befragten aus vier europäischen Ländern zeigen die Autoren, dass sich Verteidiger und Entdecker im Hinblick auf ihre Zugehörigkeitskonzepte und das Ausmaß wahrgenommener Bedrohung durch Muslime und Geflüchtete unterscheiden. Differenzen zwischen beiden Gruppen lassen sich auch für die jeweils wahrgenommene gesellschaftliche Marginalisierung und politische Repräsentation finden. Die Studie weist zudem nach, dass mit verschiedenen Positionen im Identitätskonflikt auch unterschiedliche Konzepte von Demokratie verbunden werden

Establishing a proactive safety and health risk management system in the fire service

BACKGROUND: Formalized risk management (RM) is an internationally accepted process for reducing hazards in the workplace, with defined steps including hazard scoping, risk assessment, and implementation of controls, all within an iterative process. While required for all industry in the European Union and widely used elsewhere, the United States maintains a compliance-based regulatory structure, rather than one based on systematic, risk-based methodologies. Firefighting is a hazardous profession, with high injury, illness, and fatality rates compared with other occupations, and implementation of RM programs has the potential to greatly improve firefighter safety and health; however, no descriptions of RM implementation are in the peer-reviewed literature for the North American fire service. METHODS: In this paper we describe the steps used to design and implement the RM process in a moderately-sized fire department, with particular focus on prioritizing and managing injury hazards during patient transport, fireground, and physical exercise procedures. Hazard scoping and formalized risk assessments are described, in addition to the identification of participatory-led injury control strategies. Process evaluation methods were conducted to primarily assess the feasibility of voluntarily instituting the RM approach within the fire service setting. RESULTS: The RM process was well accepted by the fire department and led to development of 45 hazard specific-interventions. Qualitative data documenting the implementation of the RM process revealed that participants emphasized the: value of the RM process, especially the participatory bottom-up approach; usefulness of the RM process for breaking down tasks to identify potential risks; and potential of RM for reducing firefighter injury. CONCLUSIONS: As implemented, this risk-based approach used to identify and manage occupational hazards and risks was successful and is deemed feasible for U.S. (and other) fire services. While several barriers and challenges do exist in the implementation of any intervention such as this, recommendations for adopting the process are provided. Additional work will be performed to determine the effectiveness of select controls strategies that were implemented; however participants throughout the organizational structure perceived the RM process to be of high utility while researchers also found the process improved the awareness and engagement in actively enhancing worker safety and health.This item is part of the UA Faculty Publications collection. For more information this item or other items in the UA Campus Repository, contact the University of Arizona Libraries at [email protected]

Effects of risperidone on auditory event-related potentials in schizophrenia

Schizophrenia is associated with cognitive deficits for which treatments remain elusive. The effects of risperidone (an antipsychotic differing in some of its pharmacological properties from typical agents) on cognitive deficits have not been extensively investigated. Mismatch negativity (MMN), N2 and P3 are cognitive event-related potentials that index preattentive (MMN) and attention-dependent information processing (N2, P3) and provide a measure of cognitive deficits in schizophrenia. The effects of risperidone treatment on MMN, N2 and P3 generation in chronic schizophrenic patients were investigated in an open- label, uncontrolled study. Risperidone treatment significantly reduced psychotic symptoms. It was associated with a decrease of peak latencies, particularly pronounced for P3. However, it did not significantly affect abnormal MMNor P3 amplitudes. The results suggest an effect of risperidone on processing speed, particularly in attention-dependent tasks. These results are in agreement with findings in recent studies on the cognitive effects of risperidone